US3447030A

US3447030A - Cold seal lamp pressure regulation

Info

Publication number: US3447030A
Application number: US619391A
Authority: US
Inventors: Lee R Gallagher; Peter D Lenn
Original assignee: Electro Optical Systems Inc
Current assignee: Electro Optical Systems Inc
Priority date: 1967-02-28
Filing date: 1967-02-28
Publication date: 1969-05-27
Anticipated expiration: 1986-05-27

Description

May 27, 1969 L, R. GALLAGHER ETAL 3,447,030

COLD SEAL LAMP PRESSURE REGULATION Filed Feb. ze, 19e? Sheetl hmm.

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May 27, 1969 L.. R. GALLAGHER ETAL 3,447,030

COLD SEAL LAMP PRESSURE REGULATION med Feb. ze, 1967 A sheet. of 2 85g l Y 5', L* "FMT ql CESIUM VPOR l l' lI Il l' I: 2`| N II k ELECTRODE 2O PRESSURE CONTROL SYSTEM United States Patent O 3,447,030 COLD SEAL LAMP PRESSURE REGULATION Lee R. Gallagher, Altadena, Calif., and Peter D. Lenn, Arlington, Va., assignors to Electro-Optical Systems, Inc., Pasadena, Calif., a corporation Vof California Filed Feb. 28, 1967, Ser. No. 619,391 Int. Cl. H011 13/28, 17/26 U.S. Cl. 315-108 7 Claims ABSTRACT OF THE DISCLOSURE This invention particularly relates to arc discharge devices of the type disclosed in copending U.S. patent application Ser. No. 501,452 filed Oct. l22, 1965, now abandoned, and assigned to the present assignee, this device being of the type wherein the arc gap electrodes are mounted within an envelope which defines a tubular volume between the envelope and each of the electrodes, each of these tubular volumes containing a quantity of the discharge material in its liquid state. Each of the t-hus formed tubular bodies of liquid is held by capillary forces and acts as a thermal barrier extending between the annular liquid-vapor interface in the vicinity of the arc and the envelope-electrode seal, the length and crosssectional area of the liquid tube being adequate to maintain a substantial temperature difference between the envelope seals and the parts of the device in the vicinity of the arc. Thus, the temperature of the device in the vicinity of the arc may be kept high with a correspondingly high vapor pressure, and the seals will be cool because of the difference established by the thermal barrier:

By utilizing a tubular volume of sutiicient length, the temperature gradient can be great enough so that ordinary mechanical envelope seals may be utilized.

The aforementioned arc discharge device structure was developed to provide more eflicient physical and thermal insulation of the envelope seals from the vaporized discharge material, thereby enabling operation at high vapor pressures and power outputs wit-h long seal life.

The present invention is directed toward a technique for controllably changing the position of the annular vapor-liquid interface in the above discussed structures without contacting the discharge material vapor, thereby enabling the device operator to conveniently control, change and/or monitor the arc pressure. In accordance with the present invention concepts the liquid discharge material is supplied to the device envelope from a pressurized storage container, pressurization of the storage container being controlled by means of a suitable pressure control system. Thus, for example, by increasing the pressure within the storage container more of the liquid discharge material is forced into the device envelope to move the annular liquid-vapor interfaces closer to the hot end of the electrodes, t-hereby increasing the vapor pressure.

Accordingly, it is an object of the present invention to provide an improved arc discharge device.

It is a primary object of the present invention to provide an improved arc-discharge device utilizing a liquid discharge material and in which the position of the liquidvapor interface during operation can be controllably changed.

It is also an object of the present invention to provide an improved vapor-electric tube.

It is another object of the present invention to provide an improved vapor-electric tube wherein the arc pressure may be conveniently controllably varied.

It is a further object of the present invention to provide an improved vapor-electric tube wherein the arc pressure -may be conveniently monitored.

It is a still further object of the present invention to provide an improved vapor-electric tube wherein the discharge material is fed in liquid form to the device envelope.

It is yet another object of the present invention to provide an improved vapor-electric tube wherein the discharge material is fed in liquid form to the device envelope from a pressurized storage container.

It is also an object of the present invention to provide an improved vapor-electric tube of the type described wherein the pressure within the storage container for the liquid discharge material is selectively variable.

The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages thereof Iwill be better understood (from the following description wherein FIGURE 1 represents the presently preferred embodiment of the invention and FIGURE 2 is an alternate embodiment of the device of FIGURE l. It is to be expressly understood, however, that the drawing is for the purpose of illustration and description only, and is not intended as a definition of the limits of the invention.

FIGURE l shows a cross-sectional view, partly in block form, of a device embodying this invention.

The arc discharge device primarily comprises a tubular envelope 10 having two

rod type electrodes

20 and 30 disposed coaxially therein. The illustrated embodiments are intended for use with cesium as the discharge material, and accordingly the envelope 10 is made of crystalline alumina, a material which is inert to cesium and which is ICC .substantially transparent to visible light and to light in the infrared and near infrared region.

The electrode 20 defines two coaxial portions, a main body portion 22 and a reduced diameter tip portion 24 which terminates in a pointed end 25. The electrode 30 similarly defines a main body portion 32 and a reduced diameter tip portion 34 terminating a pointed end 35.

The

main body portions

22 and 32 of the

electrodes

20 and 30 project through the open ends of the envelope 10 and terminate in electrical terminals 12 and 14 to I.vvhich are connected one end of

electrical leads

15 and 17. The other ends of the

electrical leads

15 and 17 are connected to a suitable power source B.

The

electrodes

20 and 30 are disposed with their pointed ends separated by a suitable gap for creating the desired discharge arc, the

electrodes

20 and 30 of the illustrated embodiment being made of tungsten.

Mechanical end seals

18 and 19 are provided to seal the ends of the envelope 10 about the

electrodes

20 and 30, the seals being fabricated of steel. The seals are provided with suitably sized circular openings through which the main -body portions of the electrodes are press fitted and then soldered to complete the seal therebetween. A pair of nitrile rubber O-

rings

41 and 42 are provided to complete the seal to the envelope 10.

The diameter of the -

main body portions

22 and 32 of the

electrodes

20 and 30 is a predetermined amount less than the inside diameter of the tubular envelope 10 so that the liquid discharge material will be contained in the resulting tubular volume by capillary forces. The drawing is not intended to be to scale and the tubular bodies of liquid cesium in the envelope are shown to be relatively thick in order to clearly depict the meniscuses at the liquid- Vapor interfaces. The main body portions o f the electrodes may be provided with radially extending insulating projections (not shown) to maintain the coaxial alignment of the electrodes within the envelope.

Closed receptacles 50 and 60 each contain a quantity of the discharge material in its liquid state, for example cesium. A feed pipe 51 interconnects the receptacle S0 with one end of the envelope 10 for feeding the liquid cesium into the tubular volume surrounding the main body portion 22 of the electrode 20, a feed pipe 61 interconnecting the receptacle 60A with the other end of the envelope 10 for feeding the liquid cesium into the tubular volume surrounding the main body portion 32 of the electrode 30. The feed pipes 51 and 61 pass through suitable apertures in the

respective end seals

18 and 19. Alternatively, a single closed receptacle can be used in conjunction with a single feed pipe and an insulated joint (capillary connection) coupling the reservoir of liquid discharge material to both ends of the tube. This alternative embodiment is shown in FIGURE 2 wherein 70 is the single closed receptacle and 71 is the single 'feed pipe connected to

capillary feed pipes

72 and 73. Electrically, the discharge device is operated such that the resistance path through the arc is much lower than the resistance path through the liquid discharge material in the feed pipes. The resistance of the liquid discharge material can be increased by making the capillary feed pipes of smaller diameter and/r increasing their length. In FIGURE 2, the diameter of

pipes

72 and 73 have been increased for purposes of illustration, but it should be understood that they are meant to represent capillary connections. However, it is presently preferred to use separate receptacles and feed pipes to absolutely insure electrical isolation.

A pressure control systems, generally indicated by the reference numeral 55, is provided to pressurize the receptacles 50 and 60 with a cold gas atmosphere, such as argon or helium for example. The pressure control system 55 is adjustable so that the gas pressure within the receptacles 50 and 60 can be controllably varied. By increasing the ambient gas pressure within the receptacles 50 and '60, more of the liquid cesium will be forced through the feed pipes 51 and 61 and into the ends of the envelope 10, thereby moving the annular liquid-vapor interfaces closer to the electrode tips, which results in an increase in the vapor pressure. Thus, use of the pressure control system to pressurize the liquid metal supply enables selective control of the position of the liquid-vapor interface during device operation. Hence, the arc pressure may be controlled, changed and/or monitored during the device operation.

To begin device operation, the pressure control system 55 is adjusted to charge the tube 10 with a predetermined amount of cesium. An electrical potential is applied across the terminals y12 and 14 to create an arc across the gap between the

pointed electrode ends

25 and 35, The heat from the arc vaporizes the cesium which ionizes and creates a self-sustaining discharge arc. Upon vaporization some of the cesium condenses on the relatively cool surfaces of the alumina envelope and the main body portions olf the electrodes and 30, the condensed liquid being held in the tubular volume between the envelope( and electrode main body portions by capillary forces. Much of the heat generated from the arc will be conducted by the liquid cesium in the tubular volume through the walls of the envelope 10 to the ambient atmosphere. Suflicient heat is removed so that the

end seals

18 and 19 remain relatively cool, yet the temperature in the arc region remains sufiicently high to prevent condensation of the cesium.

Thus there has been described a system for controlling the position of the annular vapor-liquid interface in an arc discharge device of the type wherein the arc gap electrodes are mounted within an envelope defining a tubular volume between the envelope and each of the electrodes, these tubular volumes containing discharge material in its liquid state with the liquid held by capillary forces. Although the hereinabove presented structural embodiment utilizes a cylindrical tubular envelope and rod type electrodes, any other envelope and electrode configurations may be utilized which will produce a tubular sheath of liquid discharge material about the electrodes and of sufficient length to provide the desired temperature gradi ent. Also, the present invention system concept is applicable for use with any suitable vaporizable discharge material that can be conveniently contained in liquid form, and those skilled in the art will appreciate the various structural materials suitable for use with a given discharge material. Furthermore, it is contemplated that the receptacles 50 and 60, and the feed pipes 51 and 61 be provided with controlla-ble heating means to maintain them at the temperature necessary to hold the therein contained discharge material in its liquid state.

Thus, although the invention has been described with a certain degree of particularily, it is understood that the present disclosure has been made only by way of example and that numerous changes in the combination and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed.

What is claimed is:

1. In an arc discharge device of the type wherein an elongate arc gap electrode is mounted within an elongate portion of an envelope to define a tubular volume therebetween, the tubular volume containing a quantity of discharge material in its liquid state to form an annular liquid-vapor interface during device operation, the improvement comprising:

(a) a closed receptacle containing a quantity of said discharge material in its liquid state;

(b) feed pipe means connecting said receptacle with said tubular volume in the elongate portion of said envelope;

(c) means -for pressurizing said receptacle to force some of said liquid discharge material through said feed pipe means and into said tubular volume; and

(d) means for controlling the pressure within said receptacle to thereby control the amount of said liquid discharge material within said volume and hence for controlling the position of the liquid-vapor interface during device operation.

2. In an arc discharge device as specified in claim 1, wherein the envelope is of cylindrical tubular configuration and said arc gap electrode is a rod coaxially mounted therein.

3. In an arc discharge device of the type wherein a pair of elongate arc gap electrodes are coaxially mounted in spaced apart relationship in separate elongate portions of a tubular envelope to define a tubular volume between each of said electrodes and the adjacent portions of said envelope, each tubular Volume containing a quantity of discharge material in its liquid state to form an annular liquid-vapor interface during device operation, the improvement comprising:

(b) feed pipe means connecting said receptacle with the tubular volume in each of said separate elongate portion of said envelope;

(c) means for pressurizing said receptacle to force some of said liquid discharge material through said tfeed pipe means and into said tubular volumes; and

(d) means for controlling the pressure within said receptacle to thereby control the amount of said liquid discharge material within said volumes and hence for controlling the position of the liquid-vapor interfaces during device operation.

4. In an arc discharge device of the type wherein a pair of elongate arc gap electrodes are coaxially mounted in spaced apart relationship in separate elongate portions of a tubular envelope to define a tubular volume between each of said electrodes and the adjacent portions 0f said envelope, each tubular volume containing a quantity of discharge material in its liquid state to form an annular liquid-vapor interface during device operation, the irnprovement comprising:

(a) a first closed receptacle containing a quantity of said discharge material in its liquid state;

('b) a second closed receptacle containing a quantity of said discharge material in its liquid state;

(c) first feed pipe means connecting said first receptacle With the tubular volume in one of said elongate portions of said envelope;

(d) second feed pipe means connecting said second receptacle with the tubular volume in the other of said elongate portions of said envelope;

(e) means for pressurizing said first and second receptacles to force some of said liquid discharge material through said first and second feed pipe means and into said tubular volumes; and

(f) means -for controlling the pressure within said first and second receptacles to thereby control the amount of said liquid discharge material within said volumes and hence for controlling the position of the liquidvapor interfaces during device operation.

5'. In an arc discharge device as specified in claim 3, wherein said envelope is of cylindrical tubular configuration and said arc gap electrodes are rods coaxially mounted therein.

6. In an arc discharge device as specified in claim 4, wherein said envelope is of cylindrical tubular configuration and said arc gap electrodes are rods coaxially mounted therein.

7. The arc discharge device of claim 3 wherein said feed pipe means comprises a single conduit connected to said receptacle, said conduit connected at the end opposite from said receptacle to first and second capillary conduits, each of said capillary conduits being connected to one end of said envelope for admitting liquid discharge material to said tubular volumes.

References Cited UNITED STATES PATENTS 7/ 1911 Weintraub s 313-43 X 2/1968 Rogers et al. 313-231 X U.S. Cl. X.R.